Root Awakening

Seashore lily’s sap can cause irritation
Seashore lily’s sap can cause irritationPHOTO: TAN GEK PAR
Passionfruit vine needs more sunlight
Passionfruit vine needs more sunlightPHOTO: ANG SIEW TAN
Lantana camara likely to have infection
Lantana camara likely to have infectionPHOTO: LOW W.K.
Rose cactus seen as medicinal plant
Rose cactus seen as medicinal plantPHOTO: JENNY PHANG
Engage arborist to check on health of tree
Engage arborist to check on health of treePHOTO: S.C. TAN

Seashore lily's sap can cause irritation

What is the name of this plant and is its fruit edible?

Tan Gek Par

The plant is likely the seashore lily (Crinum asiaticum). It is a native plant of Singapore and is found growing along coastal habitats. It is used as a candidate for planting up local landscapes.

Do note that all parts of the plant are toxic when ingested. When pruning it, avoid coming into contact with the sap as it may cause skin irritation for some individuals.


Passionfruit vine needs more sunlight

My passionfruit has been growing in a big pot and on the balcony for five years, but has never flowered. Should I throw it away?

Ang Siew Tan

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  • As part of the Singapore Garden Festival (SGF) 2018, to be held at Gardens by the Bay from July 21 to Aug 3, horticulturist Wilson Wong will give a talk on common garden pests and diseases followed by a plant clinic. SGF ticket-holders can take along photos of their diseased plants to find out how to treat them.

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Insufficient sunlight could be a reason for the lack of flowers in your passionfruit vine. It is a plant that needs to be grown in a location with at least six hours of direct sunlight.

You may want to provide more climbing support so that the individual stems can spread out. The current bunching of leaves and stems only creates shade within the canopy.

Also, try not to cut the vines too frequently as flowers are produced on new growth. Finally, avoid usinga fertiliser with a high nitrogen content as that will promote only the production of leaves over flowers.


Lantana camara likely to have infection

What is the name of this plant and how do I care for it? Some of its leaves at the bottom are yellow. Is this normal?

Low W.K.

The plant is known botanically as Lantana camara. Its common names include Lantana and Tickberry.

It is a popular landscaping choice due to its free-flowering nature, range of floral colours and ability to provide nectar to insects such as bees and butterflies.

This plant requires direct sunlight to grow well and does not like wet feet. It appears that your plant is grown in a high-rise balcony where sunlight is available only for several hours daily.

With the lack of sunlight and the presence of a moisture-retentive soil media, it is likely that the base of the plant has been kept wet for long periods. This can lead to fungal or bacterial infection of the lower leaves.

You can prune infected leaves. You can also consider giving the plant water by putting the pot in a saucer of water, so that the liquid is drawn up from the base of the pot. This can help to keep the base of the plant dry.

Allow the root ball to dry out a little between each watering. At the same time, try to move your plant to a brighter location to improve its growing conditions.


Rose cactus seen as medicinal plant

I saw this plant in Lim Chu Kang. What is it and is it poisonous?

Jenny Phang

The plant is the rose cactus or leaf cactus and its botanical name is Pereskia bleo. It is a common plant grown in local community gardens and can turn into a small, prickly tree. It produces attractive orange, rose-like flowers.

It is regarded as a medicinal plant as the fresh leaves are used to treat rheumatism and ulcers. Its fruit are edible too.

The rose cactus can be grown under direct sunlight or semi-shade. Unlike desert cacti, this species needs to be grown in soil that is kept moist at all times. It should never be allowed to dry out.


Engage arborist to check on health of tree

My tree has been unwell in the past one to two years. It was originally as healthy as the tree next to it. What can I do to treat and restore its health? Should I cut it down and plant a new tree of the same species? If that is a better solution, what should I look out for before planting the new tree?

S.C. Tan

It is difficult to ascertain the cause of the symptoms of dying back that are evident in your tree and it could be due to a number of reasons.

Some possibilities include root disturbance brought about by construction work, pest and disease issues and even poor pruning practices.

If you want to keep the tree and ensure its safety in the long term, it is best to consult a certified arborist who is a professional tree doctor. He can examine the tree and recommend appropriate remedial actions.

• Answers by Dr Wilson Wong, an NParks-certified practising horticulturist and park manager. He is the founder of Green Culture Singapore and an adjunct assistant professor (Food Science & Technology) at the National University of Singapore.

• Have a gardening query? E-mail it with clear, high-resolution pictures of at least 1MB, if any, and your full name to stlife@sph.com.sg

A version of this article appeared in the print edition of The Straits Times on June 09, 2018, with the headline 'Root Awakening'. Print Edition | Subscribe